(1) Field of the Invention:
The present invention relates to a process for the preparation of aromatic or furyl substituted olefins, which comprises reacting an olefinic compound with an aromatic compound or furan compound in the presence of carbon monoxide by using a rhodium carbonyl complex as a catalyst to form a corresponding aromatic or furyl substituted olefin.
(2) Description of the Prior Art:
Aromatic substituted olefinic hydrocarbons represented by styrene have heretofore been industrially prepared according to the process comprising reacting an olefin with an aromatic hydrocarbon in the presence of a Friedel-Crafts catalyst to form an aromatic substituted hydrocarbon, and then dehydrogenating the so formed aromatic substituted hydrocarbon. Needless to say, great industrial advantages would be attained if an aromatic substituted olefin could be prepared directly from an olefin and an aromatic hydrocarbon without adopting this two stage process.
It is known that a palladium salt is effective for such a direct preparation process. This process using a palladium salt catalyst, however, is defective in that the reduced palladium is precipitated and the yield of the product per unit amount of the catalyst is low. Various attempts have been made to improve reaction conditions or catalysts, for example, by adding a promotor represented by an oxidant for controlling precipitation of palladium (see, for example, Japanese Patent Publication No. 14496/76). However, satisfactory results can hardly be obtained by these attempts. Furthermore, olefins applied to this reaction using a palladium salt as a catalyst are limited to those having a relatively simple structure, such as ethylene and styrene, and olefins having a functional group have hardly been applied to this reaction and if applied, the yield are very low (see I. Moritani and Y. Fujiwara, Synthesis, 524 (1973)).
It is known that an alkenylfuran can be obtained if furan is reacted with an olefinic compound in the presence of a palladium salt catalyst. For example, when furan is reacted with methyl acrylate or acrylonitrile, methyl (2-furyl)acrylate or (2-furyl)acrylonitrile is synthesized (see O. Maruyama, Y. Fujiwara and H. Taniguchi, Preprints II, 3L 14, The 37th Annual Meeting of The Chemical Society of Japan, April, 1978).
This process for synthesizing alkenyl substituted furan compounds by direct reaction between furan and olefinic compounds has attracted attention in the art, because the reaction course in this process is greatly shortened as compared with the reaction course in the conventional process requiring numerous steps. This process, however, is still defective in that applicable furan compounds and olefinic compounds are limited to specific compounds and the yield per unit amount of the catalyst is very low.